A search for chaos in the optical light curve of a blazar: W2R 1926+42

Bachev, R.; Mukhopadhyay, Banibrata; Strigachev, A.

doi:10.1051/0004-6361/201425563

Cited by 8 publications

(14 citation statements)

References 23 publications

(32 reference statements)

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“…In this case we consider the variability of the emitted X-ray photons as plausibly intrinsic to the corona or due to the position of the corona relative to the hole (which may be a stochastic rather than a deterministic effect). The optical emission on the other hand is known to be produced from the optically thick, geometrically thin accretion disc and according to Bachev et al (2015), one way to account for the apparently stochastic optical lightcurve is to invoke a large number of active zones or emitting blobs. This implies that the overall lightcurve will be stochastic in nature irrespective of the exact injection mechanism in each zone.…”

Section: Timing Analysismentioning

confidence: 99%

Spectral and time series analyses of the Seyfert 1 AGN: Zw 229.015

Adegoke

Rakshit

Mukhopadhyay

2016

Mon. Not. R. Astron. Soc.

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We analyse the spectra of the archival XMM-Newton data of the Seyfert 1 AGN Zw 229.015 in the energy range 0.3 − 10.0 keV. When fitted with a simple power-law, the spectrum shows signatures of weak soft excess below 1.0 keV. We find that both thermal comptonisation and relativistically blurred reflection models provide the most acceptable spectral fits with plausible physical explanations to the origin of the soft excess than do multicolour disc blackbody and smeared wind absorption models. This motivated us to study the variability properties of the soft and the hard X-ray emissions from the source and the relationship between them to put further constraints on the above models. Our analysis reveals that the variation in the 3.0 − 10.0 keV band lags that in the 0.3 − 1.0 keV by 600 +290 −280 s, while the lag between the 1.0 − 10.0 keV and 0.3 − 1.0 keV is 980 +500 −500 s. This implies that the X-ray emissions are possibly emanating from different regions within the system. From these values, we estimate the X-ray emission region to be within 20R g of the central supermassive black hole (where R g = GM/c 2 , M is the mass of black hole, G the Newton's gravitational constant and c the speed of light). Furthermore, we use XMM-Newton and Kepler photometric lightcurves of the source to search for possible nonlinear signature in the flux variability. We find evidence that the variability in the system may be dominated by stochasticity rather than deterministic chaos which has implications for the dynamics of the accretion system.

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Section: Timing Analysismentioning

confidence: 99%

Spectral and time series analyses of the Seyfert 1 AGN: Zw 229.015

Adegoke

Rakshit

Mukhopadhyay

2016

Mon. Not. R. Astron. Soc.

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“…On January 11, 2015, (MJD 57033) the near-infrared (NIR) photometry reported an increase of its flux by a factor of 2.5 in the NIR band in a rather short lapse of 12 days (Carrasco et al 2015;Chandra et al 2015b). During the night of 18 January 2015 (MJD 57040), the source was detected at its highest brightness so far, with R band magnitude ∼11.71 (Bachev & Strigachev 2015). The TeV observations triggered to follow the exceptionally high optical state detected the source at energies above 150 GeV (Mirzoyan 2015) and went on until the flaring activity faded away.…”

Section: Introductionmentioning

confidence: 99%

Multi-wavelength characterization of the blazar S5 0716+714 during an unprecedented outburst phase

Ahnen¹,

Ansoldi²,

Antonelli³

et al. 2018

A&A

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Context. The BL Lac object S5 0716+714, a highly variable blazar, underwent an impressive outburst in January 2015 (Phase A), followed by minor activity in February (Phase B). The MAGIC observations were triggered by the optical flux observed in Phase A, corresponding to the brightest ever reported state of the source in the R-band. Aims.The comprehensive dataset collected is investigated in order to shed light on the mechanism of the broadband emission. Methods. Multi-wavelength light curves have been studied together with the broadband spectral energy distributions (SEDs). The sample includes data from Effelsberg, OVRO, Metsähovi, VLBI, CARMA, IRAM, SMA, Swift-UVOT, KVA, Tuorla, Steward, RINGO3, KANATA, AZT-8+ST7, Perkins, LX-200, Swift-XRT, NuSTAR, Fermi-LAT and MAGIC. Results. The flaring state of Phase A was detected in all the energy bands, providing for the first time a multi-wavelength sample of simultaneous data from the radio band to the very-high-energy (VHE, E > 100 GeV). In the constructed SED, the Swift-XRT+NuSTAR data constrain the transition between the synchrotron and inverse Compton components very accurately, while the second peak is constrained from 0.1 GeV to 600 GeV by Fermi+MAGIC data. The broadband SED cannot be described with a one-zone synchrotron self-Compton model as it severely underestimates the optical flux in order to reproduce the X-ray to γ-ray data. Instead we use a two-zone model. The electric vector position angle (EVPA) shows an unprecedented fast rotation. An estimation of the redshift of the source by combined high-energy (HE, 0.1 GeV < E < 100 GeV) and VHE data provides a value of z = 0.31 ± 0.02stats ± 0.05sys, confirming the literature value. Conclusions. The data show the VHE emission originating in the entrance and exit of a superluminal knot in and out of a recollimation shock in the inner jet. A shock–shock interaction in the jet seems responsible for the observed flares and EVPA swing. This scenario is also consistent with the SED modeling.

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“…Finally, most recently Bachev et al (2015) analyzed a long (1.6 year), densely sampled (160 000 points) optical Kepler LC of the BL Lac W2R 1926+42. They aimed to constrain the correlation dimension of the reconstructed phase-space trajectory, however the dimension did not saturate at any value smaller than the maximal tested embedding dimension 𝑚 = 10.…”

Section: Introductionmentioning

confidence: 99%

Searching for signatures of chaos in gamma-ray light curves of selected Fermi-LAT blazars

Ostapenko,

Tarnopolski,

Żywucka

et al. 2021

Preprint

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Blazar variability appears to be stochastic in nature. However, a possibility of low-dimensional chaos was considered in the past, but with no unambiguous detection so far. If present, it would constrain the emission mechanism by suggesting an underlying dynamical system. We rigorously searched for signatures of chaos in Fermi-Large Area Telescope light curves of 11 blazars. The data were comprehensively investigated using the methods of nonlinear time series analysis: phase-space reconstruction, fractal dimension, maximal Lyapunov exponent (mLE). We tested several possible parameters affecting the outcomes, in particular the mLE, in order to verify the spuriousness of the outcomes. We found no signs of chaos in any of the analyzed blazars. Blazar variability is either truly stochastic in nature, or governed by high-dimensional chaos that can often resemble randomness.

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A search for chaos in the optical light curve of a blazar: W2R 1926+42

Cited by 8 publications

References 23 publications

Spectral and time series analyses of the Seyfert 1 AGN: Zw 229.015

Spectral and time series analyses of the Seyfert 1 AGN: Zw 229.015

Multi-wavelength characterization of the blazar S5 0716+714 during an unprecedented outburst phase

Searching for signatures of chaos in gamma-ray light curves of selected Fermi-LAT blazars

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